This is the most musically-relevant way of treating the data (MIDI notes on a timeline - who cares what region they're in) and would dispense with the whole thing about having to shift-click multiple regions in the Arrange to select them just so a linked piano roll window shows their data. In fact it would be great if Logic gave the piano roll editor a 'region-agnostic' mode - i.e., like in DP, from a side-panel you select what *tracks* you want it to look at - multiple ones if desired - and it shows the contents of them, without regard for the region objects the data is in. I love Logic, it's my DAW of choice after having tried most of them, but dave M has a point.
![pro tools vs logic pro tools vs logic](http://4.bp.blogspot.com/_EMM4IuTpxkA/SsMp6RdB6zI/AAAAAAAAAHk/0t6PYF1ei4w/s320/logic9-screen.png)
Selecting a note for a part would then return the display to 2-D for editing. What I'd really love to see is Logic incorporate a 3-dimensional display for the piano roll, where, when multiple parts are selected, the display can be 'rotated' obliquely so that different parts are displayed along the Z-axis. This lack of accessibility is something that's bothered me but only on rare occasion, since it's not often that I'll edit more than one part at a time in the piano roll. Unless you move the covering note out of the way temporarily, or, should the beginning or end of the covered-up note peeks out from behind the other one (because it starts earlier or ends later) allowing you to grab a hold of it, well, you're out of luck. If you had a unison line played with even two instruments in unison, notes of one part will overlay the other in the display.
![pro tools vs logic pro tools vs logic](https://i.ytimg.com/vi/XuiSgHW9NDE/maxresdefault.jpg)
While it's possible to edit multiple regions in the piano roll, it's not well-equipped for the task. As to link modes helping with what Dave described.